Hydroxylamine and the saturated cyclic ketoximes, especially cyclohexanone oxime are successive products in the production of lactams, used in the manufacture of polyamidic synthesis fibers.
Hydroxylamine is still produced by noncatalytic small-yield processes, as for instance the Raschig process, obtaining by-products of limited utility. Recently, the more advantageous catalytic processes have been used to an increasing extent. In the majority of these known catalytic processes, hydroxylamine is produced by the hydrogenation of nitrogen monoxide, with hydrogen, in the presence of a strong acid, especially hydrochloric, sulphuric or phosphoric acid, and of a catalyst of the platinum group.
These processes have several disadvantages. Thus, they manifest relatively large consumptions of raw materials such as nitrogen monoxide, hydrogen, and mineral acid. The process yields a mixture of ammonium and hydroxylammonium salts of the acid used; these are employed in the subsequent oximation.
The saturated cyclic ketoximes, especially cyclohexanone oxime, are produced from the above-mentioned mixture of ammonium and hydroxylammonium salt of the above mineral acid, and from the respective ketone, in general by neutralization with ammonia. An aqueous solution of the ammonium salt remains after the separation of the ketoxime; it is concentrated and crystallized; the resulting product may be sold as a fertilizer of limited utility.
In hydroxylamine production by noncatalytic processes, the mixture of ammonium and hydroxylammonium salts, which is used in the oximation process, is more acidic than that resulting from our invention, so that the ammonia consumption in neutralization increases and, consequently the quantity of the recoverable ammonium salt also increases.